Integrated circuits (ICs) are typically assembled into packages by physically and electrically coupling them to a substrate made of organic or ceramic material. One or more ICs or IC packages can be physically and electrically coupled to a substrate such as a printed circuit board (PCB) or card to form an “electronic assembly”. The “electronic assembly” can be part of an “electronic system”. An “electronic system” is broadly defined herein as any product comprising an “electronic assembly”.
Examples of electronic systems include computers (e.g., desktops, laptops, hand-helds, servers, Web appliances, routers, etc.), wireless communications devices (e.g., cellular phones, cordless phones, pagers, personal digital assistants, etc.), computer-related peripherals (e.g., printers, scanners, monitors, etc.), entertainment devices (e.g., televisions, radios, stereos, tape and compact disc players, video cassette recorders, camcorders, digital cameras, MP3 (Motion Picture Experts Group, Audio Layer 3) players, video games, watches, etc.), and the like.
In the field of electronic systems there is an incessant competitive pressure among manufacturers to increase the performance of their equipment. This is particularly true regarding the packaging of ICs on substrates, where each new generation of packaging must provide increased performance, particularly in terms of an increased number of components and higher clock frequencies, while generally being smaller or more compact in size.
An IC substrate may comprise a number of insulated metal layers selectively patterned to provide metal interconnect lines (referred to herein as “traces”), and one or more electronic components mounted on one or more surfaces of the substrate. The electronic component or components are functionally connected to other elements of an electronic system through a hierarchy of electrically conductive paths that include the substrate traces. The substrate traces typically carry signals that are transmitted between the electronic components, such as ICs, of the system.
As the internal circuitry of high performance ICs, such as processors, operates at higher and higher clock frequencies, noise in the power and ground lines increasingly reaches an unacceptable level. This noise can arise due to inductive and capacitive parasitics, for example, as is well known. To reduce such noise, capacitors known as decoupling or by-pass capacitors are often used to provide a stable signal or stable supply of power to the circuitry.
As electronic devices continue to advance, there is an increasing need for higher levels of capacitance at reduced inductance levels for decoupling, power dampening, and supplying charge. In addition, there is a need for capacitance solutions that do not interfere with package connectors of various types, and which do not limit the industry to certain device sizes and packing densities. Accordingly, there is a need in the art for alternative capacitance solutions in the fabrication and operation of electronic devices and their packages.
Many types of capacitors are known in the electronic arts. One known type of capacitor used in electronic assemblies is referred to a “chip capacitor”. Chip capacitors are known, for example, in dual-terminal configurations. FIG. 1 is a prior art dual-terminal chip capacitor 1. These are currently available in a number of different sizes, such as “0402”, i.e. 0.040″×0.020″ (approx. 1.0 mm×0.50 mm). 0402 capacitors typically have a wrap-around terminal on each end, i.e. a terminal 2 or 3 covers each end and a portion of each side. One terminal 2 is of a first polarity, and the other terminal 3 is of a second polarity.
In addition to dual-terminal chip capacitors, another type of chip capacitor is referred to as an “interdigitated capacitor”. FIG. 2 is a prior art interdigitated capacitor 4 having several terminals 5–8 on each of two sides. Terminals 5 and 7 are of a first polarity type, and terminals 6 and 8 are of a second polarity type. Terminals of the same polarity type are alternated along two opposing sides of capacitor 4. Interdigitated, multilayer, ceramic capacitors are commercially available from AVX, Myrtle Beach, S.C., whose URL is currently www-avxcorp-com; TDK Corporation, Mount Prospect, Ill., whose URL is currently www-tdk-com; and Murata Electronics, Smyrna, Ga., whose URL is currently www-murata-com. (To avoid inadvertent hyperlinks, the periods in the preceding URLs have been replaced by hyphens.)
Dual-terminal chip capacitors and interdigitated caps, while adequate for many packaging and other electronic applications, are not versatile enough to accommodate the design and performance requirements of many current electronic applications, including the packaging of high performance ICs.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a significant need in the art for improved multi-terminal capacitors, for improved electronic assemblies incorporating such multi-terminal capacitors, and for improved methods of fabricating such multi-terminal capacitors and electronic assemblies.